1. Field of the Invention
The present invention relates to a bag, particularly to a bag for bulk storage and transport of materials, notably particulate solids materials. The invention also provides a device for modifying conventional bags.
2. Description of the Prior Art
Bags for storage and transport of bulk materials, for example half-tonne, one-tonne, or two-tonne capacity bags, are typically of generally cuboid shape, formed from a fabric material such as polypropylene. Typically, the weight of fabric material will be from about 180 g/m2 to 400 g/m2 depending on the intended load and operating conditions. The fabric may be reinforced for extra strength.
The bags have a top which is either permanently fully open or which can be opened, for loading. The bottoms of the bags are typically provided with a discharge spout through which the contents of the bag can be emptied when the spout is opened. Alternatively, the base of the bag may be openable for discharge of the contents.
To enable such bags to be lifted and manoeuvred by a fork-lift truck, each bag is typically provided with a lifting loop at each corner. To lift a filled bag, a fork-lift operator brings the tines of the fork close to the top of one edge of the filled bag so that each tine is adjacent to a lifting loop. An assistant lifts up each lifting loop to enable a tine to pass through the loop while the operator moves the tines forward over the bag. The fork-lift operator moves the tines further over the top of the bag until the tines are adjacent the rear pair of lifting loops, and the process is repeated so that the tines are disposed through the rear lifting loops. The bag can then be lifted and moved.
A problem with this procedure is that there is a danger of injury to the assistant when the tines or the fork are moved. This is a particular problem when filled bags are stacked high, on top of each other. The fork-lift operator is unable to see the rear pair of lifting loops when the stack is too high, and the assistant may be injured by a tine or pushed off a ladder. It is also costly to employ two men to secure the bag on the fork.
If no assistant is present, the fork-lift operator must move the truck so that the tines of the fork are positioned near the front loops. He must then get out of the cab of the truck, hook the front loops over the tines, and get back in the cab. He must then drive the truck forward as far as he thinks necessary, get out again, hook the rear loops onto the tines (if he has judged the forward distance correctly), get back in the cab, drive further forward to pick up the bag. The procedure is slow and can be dangerous.
To facilitate lifting of a bag, it has been proposed in EP 0 259 230 to provide a rigid tubular cruciform structure to be secured in the loops of a bag so that pairs of tubes can receive the tines of a fork. In FR 2 721 304 it has been proposed to provide a similar disposable structure made of cardboard. To reduce the load to which lifting loops are subjected it has been proposed to provide bags with integral lifting slings along opposite top edges so that the load is spread out along those edges; see for example GB 1 549 448, GB 2 050 298, and GB 2 092 990. However, the use of such slings does not remove the need for a fork-lift operator either to leave the cab of his truck or to use an assistant to hook the tines of the fork-lift in the slings.
According to an aspect of the present invention there is provided a collapsible bag for the storage and transport of bulk materials, as specified in claim 1.
Another aspect of the invention provides a collapsible bag for the storage and transport of bulk materials.
Resilient tubular members function as guides for the tines of a fork-lift so that, once the tines have been inserted into one end of the tubular member, full insertion of the tines through the tubular members can be accomplished with-out an assistant and without the need for a fork-lift truck operator to leave the truck.
Because the tubular members are resilient, they lie flat when under load, for example when other filled bags are stacked on top, but revert to a predetermined sectional shape when the-load is removed. This allows stacking of bags without significant wasted space, and permits lifting and moving of the bags by a fork-lift operator without an assistant.
Rigid connection of tubular members ensures that they are spaced apart from each other by a predetermined distance so that the tines of a fork, suitably spaced apart, can be inserted into the tubular members without undue difficulty. The term xe2x80x9crigidxe2x80x9d is used herein to denote a linkage which is sufficiently stiff to maintain the necessary separation between the tubular members. The skilled person will therefore appreciate that the spacers therefore need not be totally unyielding, particularly where the tubular members are dimensioned to allow some tolerance for receiving the tines of a fork-lift. The spacers may be made from any suitable structural material. Suitable materials include metals or structural plastics materials, for example nylon or an injection-moulded plastics material.
The tubular members may carry load along their length when the filled bag is suspended, or strong points in the tubular members may take the load of a filled bag, so that other regions of the tubular members need not be substantially load carrying.
The tubular members may be secured in relation to the top edges of at least some of the side panels by direct attachment to the edges, for example by sewing, gluing or riveting, or they may be formed integrally with the edges as will be further described below.
Alternatively, the tubular members may be secured in relation to the edges by means of lifting loops on a conventional bag.
In a particularly preferred embodiment, the bag is formed from a conventional bag with a lifting loop at each corner, by fitting an insert to the bag and securing it by means of the lifting loops. The insert comprises a pair of substantially parallel resilient tubular members which are connected together at or adjacent to each end by rigid spacing means. To provide strong points, it is preferred that the tubular members have laterally extending slots or apertures on their upper surfaces for receiving the lifting loops, and the tubular members are of sufficient size that at least the top portion of each loop is disposed inside a tubular member when the insert is fitted on the bag. The tubular members thus function as guides for the tines of a fork-lift, but the lifting loops take the load when the bag is lifted on the tines.
Accordingly, another aspect of the present invention comprises a device for securing to a bag for the storage and transport of bulk materials, as specified in claim 11.
The tubular members may be made from any suitable resilient material, for example a natural or synthetic rubber material. A preferred material is vulcanised rubber, or the sort of rubber that Wellington boots are typically made from.
The inside surfaces of the tubular members may optionally be provided with a tough coating to confer resistance to cutting and scratching by the tines of a fork-lift.
It will be appreciated that the tubular members may be of any cross sectional shape which will accept the tines of a fork-lift or the like. For example the tubular members may be circular, rectangular, square or oval in cross section. For convenience hereinafter, the invention will be described with reference to tubular members which are substantially circular in section. However, it is to be understood that the invention is not limited to this embodiment.
The tubular members may be of any suitable diameter to receive a tine of a fork-lift, for example they may have a diameter in the range 100 to 300 mm, notably about 200 mm.
Although it is preferred to make the bag by modifying an existing conventional bag as described above, the bags can be made by other methods. For example, the tubular members may be manufactured separately and subsequently secured to opposite top edges of the box by securing means, for example stitching. The rigid connecting means may be secured to the tubular members either before or after the tubular members are secured to the edges of the box. In another embodiment, the tubular members are formed from the material of the bag so that the tubular members are integral parts of the bag. This may be achieved, for example, by forming the bag with a pair of opposed sides which are longer than the other pair of opposed sides, and forming the extra length into tubes. A preferred material is polypropylene fabric. The tubular members may be reinforced by incorporation of a rubber material, to impart resilience. The rubber material may be secured to the tubular members by any suitable securing means, for example stitching or gluing.
Accordingly, a further aspect of the invention provides a method of manufacturing a collapsible bag for the storage and transport of bulk materials as specified in claim 13.
Resilience may also be imparted by reinforcing the tubular member with a suitable reinforcing member, for example a wire of metal or plastics material which is helically wound around the tubular member.
Additionally or alternatively, the tubular members may be placed on a former to define a preferred shape and/or configuration, and sprayed with a fluid material that dries to a form-retaining coating to retain them in that preferred shape and/or configuration. The fluid material may be a foam or a lacquer.